Toner binder resin and static charge developing toner using the resin

ABSTRACT

A static charge developing toner excelling in resistance to offset and low-temperature fixing property and using as at least part of a binder resin component an epoxy resin-including binder resin which is obtained by polymerizing a polymerizable monomer in the presence of an epoxy resin.

TECHNICAL FIELD

This invention relates to a binder resin for toner and a static chargedeveloping toner using the resin. More particularly, this inventionrelates to a toner binder resin fit for the production of a staticcharge developing toner which, when used for the development of anelectrostatic latent image formed by such means as theelectrophotographic method, the electrostatic recording method, theelectrostatic printing method, and the like, can form a fixed imagestable at low temperatures and incapable of inducing offset and whichexhibits excellent stability during storage.

BACKGROUND ART

In the field of electrophotography, the heating roller method has beenwidely disseminated as a means for enabling a toner image formed on animage receiving sheet to be permanently fixed on the sheet.

This method is exceptionally fit for an electrophotographic copyingdevice because the surface of a heating roller tightly contacts theimage surface of the image receiving sheet and consequently the thermalefficiency with which the toner image is thermally fused to the imagereceiving sheet is so perfect as to permit quick fixation of the image.

In recent years, the electrophotographic copying devices of this classhave come to demand a cut in power consumption and an addition tooperating speed and have consequently created a need for a toner capableof being fixed at low temperatures.

In order that a given toner may be rendered fixable at low temperatures,the toner requires to lower the melting temperature thereof. It is,therefore, conceivable to use a resin of a low melting point such as,for example, a vinyl chloride resin as the binder resin componentincorporated in the toner or to increase the content of a (meth)acrylicester component in a styrene-(meth)acrylic resin, for example.

Indeed the use of this resin enables the melting point of the toner tobe lowered. It nevertheless has the possibility of narrowing thetemperature range in which the toner can be fixed without inducingeither low-temperature or high-temperature offset (hereinafter referredto occasionally as "non-offset range") or failing to offer a fullysatisfactory toner fixing ratio.

JP-A-61-117,564 discloses a so-called pulverized toner obtained bymelting and kneading a binder resin with a coloring agent and othercomponents and pulverizing the resultant blend and classifying theproduced particles, which pulverized toner is characterized bycontaining as basic resins 90-30% by weight of an epoxy resin having aweight average molecular weight of not less than 2000 and 10-70% byweight of a styrene-acryl resin having a weight average molecular weightof not less than 50000 for the purpose of allowing the producedpulverized toner to enjoy fully satisfactory pulverizability, avoidemitting any offensive odor during the course of fixation, manifestperfect fixability, and produce only sparing fogging during the courseof printing.

JP-A-59-129,862 discloses a flash fixing toner such that an image formedof this toner is fixed by a procedure of exposing this image to anultraviolet light of high energy and a visible radiation therebyelevating the temperature of the toner in the image instantaneously tothe melting point thereof, which flash fixing toner is obtained bycomposing a binder resin combining 100 parts by weight of an epoxy resinhaving a weight average molecular weight of 1000-10000 with 10-50 partsby weight of an ethylene-n-butyl acrylate resin having a weight averagemolecular weight of 10000-100000 for the sake of appropriateadhesiveness of the toner resin to the surface of a sensitive plate andfor the purpose of preventing the flash fixed image from producing avoid and then pulverizing the resultant binder resin.

Though it has been known in the art to use the epoxy resin as part ofthe binder resin in the toner of the kind under discussion, it has neverbeen known to the art to use the epoxy resin for the purpose of enablingthe toner to be fixed at low temperatures.

In the case of the so-called polymerized toner resorting to thesuspension polymerization, the emulsion polymerization, or the likewhich is regarded as advantageous because of the uniformity and thefineness of the toner particles, the qualities yearned for in the lightof the stability of charging of the toner and the high degree ofresolution of the toner image, it has been heretofore considereddifficult to incorporate the epoxy resin mentioned above in thispolymerized toner by reason of the method of polymerization used for theepoxy resin.

DISCLOSURE OF THE INVENTION

This invention, therefore, has for an object thereof the provision of animproved binder resin for toner and a static charge developing tonerusing the binder resin. This invention has another object of providingthe binder resin for the production of a low-temperature fixing tonerwhich excels in resistance to offset, fixing property, and stabilityduring storage.

The objects mentioned above are accomplished by a toner binder resinincluding an epoxy resin, which binder resin is obtained by polymerizinga polymerizable monomer in the presence of the epoxy resin.

In the epoxy resin-including toner binder resin according to thisinvention, the epoxy resin appropriately has an epoxy equivalent in therange of 100-1000 g/equivalent weight.

Further in the epoxy resin-including toner binder resin according tothis invention, the epoxy resin is appropriately contained in aproportion in the range of 1-25%, based on the total weight of the tonerbinder resin.

In the epoxy resin-including toner binder resin according to thisinvention, the polymerizable monomer appropriately is a styrenic monomerand/or a (meth)acrylic ester type monomer.

The objects mentioned above are also accomplished by a toner binderresin including an epoxy resin and a crystalline (meth)acrylic estertype polymer, which binder resin is obtained by polymerizing apolymerizable monomer in the presence of the epoxy resin and thecrystalline (meth)acrylic ester polymer.

In the epoxy resin- and crystalline (meth)acrylic esterpolymer-including toner binder resin according to this invention, theepoxy resin appropriately has an epoxy equivalent in the range of100-1000 g/equivalent weight.

In the epoxy resin- and crystalline (meth)acrylic esterpolymer-including toner binder resin according to this invention,appropriately the epoxy resin is contained in a proportion in the rangeof 1-25% and the crystalline (meth)acrylic ester type polymer iscontained in a proportion in the range of 0.5-20%, based on the totalweight of the toner binder resin.

In the epoxy resin- and crystalline (meth)acrylic esterpolymer-including toner binder resin according to this invention, thepolymerizable monomer appropriately is a styrenic monomer and/or a(meth)acrylic ester monomer.

This invention further provides a toner binder resin obtained bysuspension polymerizing a polymerizable composition containing at leasta polymerizable monomer and an epoxy resin in an aqueous medium, theepoxy resin being uniformly dispersed in a polymerizable monomer.

The objects mentioned above are further accomplished by a toner binderresin characterized by using as at least part of the binder resincomponent thereof the above mentioned epoxy resin-including binder resinor the above mentioned epoxy resin- and crystalline (meth)acrylic esterpolymer-including toner binder resin.

In the static charge developing toner of this invention, the content ofthe epoxy resin in the toner composition appropriately is in the rangeof 0.5-25% by weight.

This invention further provides a static charge developing tonercharacterized by being obtained by suspension polymerizing in an aqueousmedium a polymerizable composition containing a polymerizable monomer,and a coloring agent and/or a magnetic powder, in the presence of anepoxy resin.

This invention also provides a static charge developing tonercharacterized by being obtained by suspension polymerizing in an aqueousmedium a polymerizable composition containing a polymerizable monomer,and a coloring agent and/or a magnetic powder, in the presence of anepoxy resin and a crystalline (meth)acrylic ester polymer.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, this invention will be described more specifically below withreference to embodiments thereof.

The toner binder resin of this invention achieves the intention ofimparting an improved melting property to a toner binder resin byincorporating an epoxy resin in a polymerizable monomer capable offorming a binder resin in consequence of polymerization and polymerizingthe resultant blend.

After a study, the present inventors have found that an epoxy resinincorporated as a binder resin component in a toner is capable oflowering the glass transition point of the toner but that the epoxyresin, when simply added as one constituent of the binder resincomponent, fails to improve fully the fixing property at lowtemperatures and the ability to resist offset and entails degradation ofthe stability during storage. They have been ascertained that when anepoxy resin-including toner binder resin which is obtained byincorporating an epoxy resin in a polymerizable monomer and polymerizingthe resultant blend (hereinafter referred to as "epoxy resin-includingbinder resin") is used as a binder resin component, the produced toner,probably because of enhanced uniform distribution of the epoxy resin inthe toner particles, brings about surprising effects of imparting highstability (resistance to frictional excoriation) to a produced image atthe fixing temperature, widening the nonoffset range, manifesting thelow-temperature fixing property and the resistance to offset fullysatisfactorily, and excelling in stability during storage.

The present inventors, after continuing the study, have found that atoner using a binder resin obtained by polymerizing a polymerizablemonomer in the presence of a crystalline (meth)acrylic ester typepolymer in addition to the epoxy resin mentioned above, for some unknownreason, manifests a synergistic effect of heightening thelow-temperature fixing property and enlarging the nonoffset range ascompared with the toner using some other offset-preventing agent.

Epoxy resin-including binder resin

The epoxy resin to be used in this invention is not limitedparticularly. The epoxy resins of various kinds such as, for example,bisphenol A type, halogenated bisphenol type, resorcinol type, bisphenolF type, novolac type, polyalcohol type, polyglycol type, polyolefintype, and alicyclic type which are solid or liquid at normal roomtemperatures (25° C.±2° C.) are available herein. The epoxy resin of thebisphenol A type is generally used. From the viewpoint of the stabilityof the produced toner during storage, the epoxy resin appropriately hasa glass transition point (Tg) exceeding 25° C., preferably falling inthe range of 30-60° C. If the molecular weight (Mn) of the epoxy resinis extremely high and exceeds 3000, for example, the possibility ensuesthat the polymerization of a main binder resin component to be describedspecifically hereinbelow for the formation of an epoxy resin-includingbinder resin will not profitably proceed, the produced polymer will emitthe epoxy resin from the matrix thereof, and the epoxy resin will not beuniformly dispersed in the polymer matrix. Thus the molecular weightappropriately is relatively low. Properly in the case of the bisphenol Atype, the epoxy equivalent is in the range of 100-1500 g/equivalentweight, preferably 100-1000 g/equivalent weight, and more preferably400-1000 g/equivalent weight.

In the toner binder resin of this invention, the polymerizable monomerwhich, on being polymerized, forms a binder resin component is notparticularly limited. It may be any of various vinyl monomers generallyused in the field of toners. As concrete examples of the vinyl monomerusable herein, styrenic monomers such as styrene, o-methyl styrene,m-methyl styrene, p-methyl styrene, α-methyl styrene, p-methoxy styrene,p-tert-butyl styrene, p-phenyl styrene, o-chlorostyrene,m-chlorostyrene, p-chlorostyrene, and α-methyl styrene; (meth)acrylicester type monomers such as methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate, dodecyl acrylate, stearyl acrylate,2-ethylhexyl acrylate, tetrahydrofuryl acrylate, methyl methacrylate,ethyl methacrylayte, propyl methacrylate, n-butyl methacrylate, isobutylmethacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexylmethacrylate, and stearyl methacrylate; olefinic monomers such asethylene, propylene, and butylene; and acrylic acid, methacrylic acid,vinyl chloride, vinyl acetate, acrylonitrile, acrylamide,methacrylamide, and N-vinyl pyrrolidone may be cited. Thesepolymerizable monomers may be used either singly or in the form of acombination of two or more members. Among other conceivablecombinations, those which have styrenic monomers and/or (meth)acrylicester type monomers as main components thereof prove particularlyfavorable. From the standpoint of low temperature fixing property andstability during storage, it is proper to form styrenic--(meth)acrylicester type copolymers by using styrenic monomers and (meth)acrylic estertype monomers. Further from the standpoint of the thermal properties ofthe toner formed by using the produced binder resin, it is appropriateto form a styrene-(meth)acrylic ester mixture containing not less than50% by weight of styrene.

The amount of the epoxy resin in the polymerizable composition duringthe production of the epoxy resin-including binder resin of thisinvention is not particularly limited. Appropriately in the epoxyresin-including binder resin which is obtained in consequence of thepolymerization, the epoxy resin is incorporated in a proportion in therange of 1-25%, preferably 2-20%, based on the total weight of thebinder resin. If the content of the epoxy resin is less than 1% based onthe total weight of the binder resin, the static charge developing tonerproduced by using the resultant epoxy resin-including binder resin willnot be expected to enjoy any improvement in the low-temperature fixingproperty or the ability to resist offset. Conversely, if the epoxycontent exceeds 25%, the possibility ensues that the polymerization ofthe polymerizable monomer mentioned above for the formation of the mainbinder resin component will not profitably proceed, the binder resinproduced by the polymerization will emit the epoxy resin from the matrixthereof, and the epoxy resin will not be uniformly dispersed in thebinder resin matrix.

The method of polymerization to be used in the production of the epoxyresin-including binder resin of this invention does not need to beparticularly limited but may be selected from among various knownmethods of polymerization such as suspension polymerization, emulsionpolymerization, solution polymerization, and bulk polymerization. Amongother methods cited above, the suspension polymerization method provesparticularly favorable because this method can be expected to improvethe uniform dispersibility of the epoxy resin in the produced binderresin.

The suspension polymerization is effected by suspending in an aqueousmedium the polymerizable monomer composition obtained by dispersing ordissolving such an epoxy resin as described above supplied in the formof beads, for example, in such a polymerizable monomer as describedabove and polymerizing the suspended polymerizable monomer compositionat a temperature in the range of 50-90° C., preferably 60-80° C., forexample.

In the production of the epoxy resin-including binder resin by thesuspension polymerization of the polymerizable monomer component asdescribed above, the monomer component may incorporate therein otherpolymer such as, for example, a polyester and may suitably incorporatefurther therein such known additives as a chain transfer agent servingto adjust the degree of polymerization. Further, during the course ofthe suspension polymerization, a cross-linking agent may be used.

As concrete examples of the cross-linking agent, aromatic divinylcompounds such as divinyl benzene, divinyl naphthalene, and derivativesthereof; diethylenically unsaturated carbolic esters such as ethyleneglycol dimethacrylate, diethylene glycol dimethacrylate, triethyleneglycol dimethacrylate, trimethylol propane triacrylate, allylmethacrylate, t-butyl aminoethyl methacrylate, tetraethylene glycoldimethacrylate, and 1,3-butan diol dimethacrylate; divinyl compoundssuch as N,N-divinyl aniline, divinyl ether, divinyl sulfide, and divinylsulfonic acid; and compounds having three or more vinyl groups may becited.

Further, polybutadiene, polyisoprene, unsaturated polyesters, andchlorosulfonated polyolefins are also effectively usable.

In the suspension polymerization, a dispersion stabilizer may be addedfor ensuring stabilization of the suspended particles. As concreteexamples of the dispersion stabilizer which is usable herein,water-soluble macromolecular compounds such as polyvinyl alcohol,gelatin, tragacanth, starch, methyl cellulose, carboxy methyl cellulose,hydroxy ethyl cellulose, polysodium acrylate, and polysodiummethacrylate; surfactants such as sodium dodecylbenzene sulfonate,sodium tetradecyl sulfonate, sodium pentadecyl sulfonate, sodium octylsulfonate, sodium allyl-alkyl-polyether sulfonate, sodium oleate, sodiumlaurate, sodium caprate, sodium caprylate, sodium caproate, potassiumstearate, potassium oleate, sodium 3,3'-disulfon-diphenylurea-4,4'-diazo-bis-amino-8-napthtol-6-sulfonate,orthocarboxybenzene-azo-dimethyl aniline, and sodium2,2',5,5'-tetramethyl-triphenyl methane-1,1'-diazo-bis-β-naphtholdisulfonate; and alginates, zein, casein, barium sulfate, calciumsulfate, barium carbonate, magnesium carbonate, calcium phosphate, talc,cray, diatomaceous earth, bentonite, titanium hydroxide, thoriumhydroxide, and metal oxide powders may be cited.

The dispersion stabilizer, for the purpose of enhancing the uniformdispersibility of the epoxy resin in the produced binder resin, must beused with the composition thereof and the amount of use thereof suitableadjusted so that the binder resin particles may acquire a prescribedparticle diameter such as, for example, in the range of 2-20 μm.preferably 3.5-15 μm. When a water-soluble macromolecular compound isused as the dispersion stabilizer, for example, the amount thereof to beused is properly in the range of 0.01-20% by weight, preferably 0.1-10%by weight, based on the amount of the polymerizable monomer component.When a surfactant is used, the amount thereof to be used is properly inthe range of 0.01-10% by weight, preferably 0.1-5% by weight, based onthe amount of the polymerizable monomer.

As the polymerization initiator to be used for the polymerization, anoil-soluble peroxide type or azo type initiator which is generally usedin suspension polymerization. As concrete examples of the polymerizationinitiator, peroxide type initiators such as benzoyl peroxide, lauroylperoxide, octanoyl peroxide, benzoyl orthochloroperoxide, benzoylorthomethoxyperoxide, methylethyl ketone peroxide, diisopropyl peroxydicarbonate, cumene hydroperoxide, cyclohexanone peroxide, t-butylhydroperoxide, and diisopropyl benzene hydroperoxide, and2,2'-azobis-isobutyronitrile, 2,2'-azobis(2,4-dimethylvalero-nitrile),2,2'-azobis(2,3-dimethyl butyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,3,3-trimethyl butyro-nitrile),2,2'-azobis(2-isopropyl butyronitrile),1,1'-azobis-(cyclohexane-1-carbonitrile),2,2'-azobis(4-methoxy-2,4-dimethyl valeronitrile),2-(carbamoyl-azo)isobutylonitrile, 4,4'-azobis(4-cyanovaleric acid), anddimethyl-2,2'-azobisisobutyrate may be cited. The amount of thepolymerization initiator to be used is properly in the range of 0.01-20%by weight, preferably 0.1-10% by weight, based on the amount of thepolymerizable monomer.

During the polymerization of the epoxy resin-including binder resin,such substances as an offset preventing agent, a charge controllingagent, and the like which are allowed to be incorporated in a toner aswill be described in the section "static charge developing toner"hereinbelow may be added in advance.

Binder resin including epoxy resin and crystalline (meth)acrylic estertype polymer

The binder resin including an epoxy resin and a crystalline(meth)acrylic ester type polymer according to this invention(hereinafter referred to as "epoxy resin- and crystalline (meth)acrylicester type polymer-including binder resin") is obtained by polymerizinga polymerizable monomer in the presence of an epoxy resin and acrystalline (meth)acrylic ester type polymer, namely, basically in thesame manner as the "epoxy resin-including binder resin" mentioned aboveexcepting the polymerizable monomer is polymerized in the presence of acrystalline (meth)acrylic ester type polymer in addition to the epoxyresin.

The crystalline (meth)acrylic ester type polymer to be used in thisinvention is not particularly limited. It may be a polymer whichcontains the monomer represented by the following general formula (I) asa component unit appropriately in a ratio in the range of 100-50 mol %,preferably 100-60 mol %, and more preferably 100-70 mol %. ##STR1##(wherein R is a hydrogen atom or a methyl group and n is an integer of15-32, preferably 18-32, and more preferably 21-32).

As concrete examples of the monomer represented by the general formula(I) shown above, stearyl acrylate, stearyl methacrylate, hexadecylacrylate, hexadecyl methacrylate, heptadecyl acrylate, heptadecylmethacrylate, nonadecyl acrylate, nonadecyl methacrylate, arachylacrylate, arachyl methacrylate, behenyl acrylate, behenyl methacrylate,pentacosyl acrylate, pentacosyl methacrylate, heptacosyl acrylate sic!,heptasyl methacrylate sic!, nonocosyl acrylate nonacosyl methacrylate,dotriacontyl acrylate, and dotriasyl methacrylate may be cited. Amongother monomers cited above, stearyl acrylate, behenyl acrylate, behenylmethacrylate, pentacosyl acrylate, and pentacosyl methacrylate proveparticularly favorable.

As concrete examples of the monomer which is copolymerizable with themonomer represented by the general formula (I) mentioned above, styrenicmonomers such as styrene, o-methyl styrene, m-methyl styrene, p-methylstyrene, α-methyl styrene, p-methoxy styrene, p-tert-butyl styrene,p-phenyl styrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene;noncrystalline acrylic ester type or noncrystalline methacrylic estertype monomers such as methyl acrylate, ethyl acrylate, n-butyl acrylate,isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-ethylhexylacrylate, phenyl acrylate, methyl α-chloroacrylate, ethyl methacrylate,propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate,n-octyl methacrylate, dodecyl methacrylate, and 2-ethylhexylmethacrylate; acrylic acid type monomers such as acrylonitrile,methacrylonitrile, and acrylamide; vinyl ether type monomers such asvinyl methyl ether, vinyl isobutyl ether, and vinyl ethyl ether; vinylketone type monomers such as vinyl methyl ketone, vinyl ethyl ketone,and vinyl hexyl ketone; N-vinyl compound type monomers such as N-vinylpyrrole, N-vinyl carbazole, N-vinyl indole, and N-vinyl pyrrolidone; andvarious vinyl type other monomers such as ethylene, propylene, butylene,vinyl chloride, and vinyl acetate may be cited.

The weight average molecular weight of the crystalline (meth)acrylicester type polymer appropriately is in the approximate range of35000-500000, preferably 35000-450000, and more preferably 35000-400000.If the weight average molecular weight is less than 35000, thepossibility arises that the melt viscoisity will be too low for theproduced toner to exhibit such an offset preventing effect as isexpected or for the crystalline (meth)acrylic ester type polymer tomanifest perfect dispersibility in the binder resin or for the toner toacquire perfect stability during storage. Conversely, if the weightaverage molecular weight exceeds 500000, the possibility ensues that themelt viscosity will be too high and the melting properties will be toolow for the ability to resist offset to be manifested as expected.

Incidentally, crystalline (meth)acrylic ester type polymers aredisclosed as offset preventing agents in JP-A-06-148,936,JP-A-06-194,874, JP-A-06-194,877, etc. It is permissible to use any ofthose polymers disclosed therein as the offset preventing agent herein.

The production of the epoxy resin and crystalline (meth)acrylic estertype polymer-including binder resin of this invention is attained bypolymerizing the same polymerizable monomer as described in thepreceding section in the presence of such a crystalline (meth)acrylicester type polymer as described above and the same epoxy resin asdescribed in the preceding section "epoxy resin-including binder resin."

The amount of the epoxy resin to be incorporated in the polymerizablecomposition in the production of the epoxy resin and crystalline(meth)acrylic ester type polymer-including binder resin of thisinvention is not particularly limited. For the same reason as stated inthe preceding section, it is appropriately incorporated in thepolymerizable composition such that the binder resin obtained by thepolymerization may contain the epoxy resin in an amount in the range of1-25%, preferably 2-20%, based on the total weight of the binder resin.The amount of the crystalline (meth)acrylic ester type polymer to beadded, though not particularly limited, is appropriately incorporated inthe polymerizable composition such that the binder resin obtained by thepolymerization will contain the crystalline (meth)acrylic ester typepolymer in an amount in the range of 0.5-20%, preferably 1-15%, based onthe total weight of the binder resin. If the content of the crystalline(meth)acrylic ester type polymer is less than 0.5% of the total weightof the binder resin, the effect of the addition of the crystalline(meth)acrylic ester type polymer will not be substantially perceptiblebecause the static charge developing toner produced by using theresultant binder resin will manifest such low temperature fixingproperty and offset-resisting property as are not notably different fromthose of the toner using the epoxy resin-including binder resindescribed in the preceding section. Conversely, if the content of thecrystalline (meth)acrylic ester type polymer exceeds 20%, thepossibility arises that the polymerization of the polymerizable monomerfor the formation of the main binder resin component will fail toproceed profitably, the binder resin obtained by the polymerization willemit the crystalline polymer from the matrix thereof, and thecrystalline polymer will not be uniformly dispersed in the matrix.

The method of polymerization to be used in this case, though notparticularly limited similarly to that described in the precedingsection, may be selected from among various methods of polymerization.Among other methods available, the method of suspension polymerizationproves particularly favorable because this method can be expected toimprove the uniform dispersibility of the epoxy resin and thecrystalline (meth)acrylic ester type polymer in the produced binderresin.

The suspension polymerization is effected by suspending in an aqueousmedium the polymerizable monomer composition obtained by dispersing ordissolving such an epoxy resin supplied in the form of beads, forexample, and a crystalline (meth)acrylic ester type polymer, in such apolymerizable monomer as described in the preceding section andpolymerizing the suspended polymerizable monomer composition at atemperature in the range of 50-90° C., preferably 60-80° C., forexample.

In the production of the epoxy resin- and crystalline (meth)acrylicester type polymer-including binder resin by the suspensionpolymerization of the polymerizable monomer component as describedabove, the monomer component may incorporate therein other polymer suchas, for example, a polyester and may suitably incorporate furthertherein such known additives as a chain transfer agent serving to adjustthe degree of polymerization. Further, during the course of thesuspension polymerization, a cross-linking agent may be used. Further,in the suspension polymerization, a dispersion stabilizer may be addedfor ensuring stabilization of the suspended particles. As thepolymerization initiator to be used for the polymerization, anoil-soluble peroxide type or azo type initiator which is generally usedin suspension polymerization. The specific examples and the amounts ofaddition of the polymer, additives, cross-linking agent, dispersionstabilizer, and polymerization initiator are the same as those describedin the preceding section.

During the polymerization of the epoxy resin and crystalline(meth)acrylic ester type polymer-including binder resin, such substancesas an offset preventing agent, a charge controlling agent, and the likewhich are allowed to be incorporated in a toner as will be described inthe section "static charge developing toner" hereinbelow may be added inadvance to the binder resin.

Static charge developing toner (1)

The static charge developing toner according to this invention can beobtained by using the epoxy resin-including binder resin and/or theepoxy resin- and crystalline (meth)acrylic ester type polymer-includingbinder resin as at least part of the binder resin component, suitablycombining the binder resin with a coloring agent and, when necessary,other binder resin, and additives such as an offset-preventing agent, acharge controlling agent for adjusting electric charge, and a fluidizingagent which are normally used for a standard static charge developingtoner, melting and kneading the blend, and then pulverizing theresultant solid mix, and classifying the produced powder. When the tonerto be produced is required to be magnetic in attribute, the blend mayincorporate a magnetic powder. The charge controlling agent, thefluidizing agent, and the like may be added to and attached outwardly tofine colored particles which have been obtained by pulverizing andclassifying to a prescribed particle diameter a solid blend formed ofthe other components to give rise to the toner particles aimed at.

The other binder resin which can be used, when necessary, in theproduction of the static charge developing toner of this invention maybe any of such resins as styrene type resin, (meth)acrylic ester typeresins, styrene-(meth)acrylic ester type resins, polyester type resins,olefin type resins, polyacryl amide, and polyvinyl chloride which arenormally used as toner binder resins. Among other resins mentionedabove, styrenic resins, (meth)acrylic ester type resins, andstyrene-(meth)acrylic ester type resins prove particularly favorable.

The amount of the epoxy resin which is ultimately contained in the tonerowing to the use of the epoxy resin-including binder resin and/or theepoxy resin and crystalline (meth)acrylic ester type polymer-includingbinder resin in the static charge developing toner according to thisinvention, though not limited particularly, appropriately is such thatthe epoxy resin may be contained in an amount in the range of 0.5-25%,preferably 1-20% based on the total weight of the toner. If the amountof the epoxy resin to be incorporated is less than 0.5%, the improvementin the melting properties of the toner due to the addition of the epoxyresin will not be sufficient. Conversely, if this amount exceeds 25%,the excess will not proportionately improve the melting properties ofthe toner and will possibly impair the stability of the toner particlesduring storage and the stability of cohesion of the toner particles.

The coloring agent to be incorporated in the toner is any of dyes andpigments universally known to persons of ordinary skill in the art,without reference to choice between organic and inorganic substances. Asconcrete examples of the coloring agent usable herein, carbon black,nigrosine dye, aniline blue, calco-oil blue, chrome yellow, ultra marineblue, DuPont oil red, quinoline yellow, methylene blue chloride,phthalocyanine blue, malachite green oxalate, lamp black, oil black, azooil black, and rose bengal may be cited. When necessary, two or more ofthese coloring agents may be used in combination.

As concrete examples of the magnetic powder to be added in theproduction of a magnetic toner, powders of such ferromagnetic metals asiron, cobalt, and nickel and powders of such metal compounds asmagnetite, hematite, and ferrite may be cited. These magnetic powdersfunction additionally as coloring agents in the production of a magnetictoner, such a magnetic power may be used as a coloring agent eitherindependently or in combination with the dye or pigment mentioned above.

The coloring agent or the magnetic powder may be used in the unmodifiedform. When the coloring agent to be used has the surface thereof treatedin advance by a suitable method, the produced toner is enabled to havethis coloring agent uniformly dispersed therein and this toner,therefore, proves advantageous because it is capable of forming an imageof high quality. When carbon black is to be used as the coloring agent,for example, the grafted carbon black such as carbon black graft polymerwhich has a polymer chain bound to the surface of the carbon blackparticles as disclosed in JP-A-63-207,767 and JP-A-63,265,913 provesappropriate. Even when a coloring agent other than carbon black is used,the surface-treated coloring agent which is obtained by the methoddisclosed in JP-A-01-118,573 proves appropriate.

The offset-preventing agent which is incorporated, when necessary, inthe static charge developing toner of this invention, though notparticularly limited, is a polyolefin or so-called polyolefin wax whichhas a weight average molecular weight in the approximate range or1000-45000, preferably 2000-6000, for example. As concrete examples ofthe polyolefin wax, effectively usable herein, homopolymers such aspolyethylene, polypropylene, and polybutylene, olefin copolymers such asethylene-propylene copolymer, ethylene-butene copolymer,ethylene-pentene copolymer, ethylene-3-methyl-1-butene copolymer, andethylene-propylene-butene copolymer, and copolymers of olefins withother monomers such as, for example, vinyl ethers like vinyl methylether, vinyl-n-butyl ether, vinyl phenyl ether, vinyl esters like vinylacetate and vinyl butylate, haloolefins like vinyl fluoride, vinylidenefluoride, tetrafluoroethylene, vinyl chloride, vinylidene chloride, andtetrachloroethylene, (meth)acrylic esters like methyl acrylate, ethylacrylate, n-butyl acrylate, methyl methacrylate, ethyl methacrylate,n-butyl methacrylate, stearyl methacrylate, N,N-dimethyl amino ethylmethacrylate, and t-butyl amino ethyl methacrylate, acrylic acidderivatives like acrylonitrile and N, N-dimethyl acrylamide, organicacids like acrylic acid, methacrylic acid, maleic acid, fumaric acid,and itaconic acid, and diethyl fumarate, and β-pinene may be cited.

Besides the polyolefins mentioned above, the offset-preventing agentswhich are usable herein include natural or synthetic paraffin waxes,particularly high-melting paraffin waxes having melting points in therange of 60-70° C., fatty acid metal salts, particularly higher fattyacid salts having not less than 17 carbon atoms, such as zinc salt,barium salt, lead salt, cobalt salt, calcium salt, and magnesium salt ofstearic acid, zinc salts, manganese salts, iron salts, and lead salts ofolefin acids, and zinc salt, cobalt salt, and magnesium salt of palmiticacid, higher alcohols such as myricyl alcohol, polyhydric alcohol esterssuch as glyceride stearate and glyceride palmitate, fatty acid esterssuch as myricyl stearate and myricyl palmitate, fatty partiallysaponified esters such as montanic partially saponified esters, higherfatty acids such as stearic acid, palmitic acid, and montanic acid;fatty acid amides such as ethylene bis-stearoyl amide, and mixturesthereof, for example.

Further, as an offset-preventing agent, such a crystalline (meth)acrylicester type polymer as described in the preceding section "binder resinincluding epoxy resin and crystalline (meth)acrylic ester type polymer"may be used as separately added subsequently to the polymerization ofthe binder resin. The use of the crystalline (meth)acrylic ester typepolymer can be expected to improve various properties such asoffset-resisting property, mold release property, fluidity, and chargeinitiating property.

As concrete examples of the charge controlling agent, nigrosine, monoazodye, zinc, hexadecyl succinate, alkyl esters or alkyl amides ofnaphthoeic acid, nitrofumic acid, N,N-tetramethyl diamine benzophenone,N,N-tetramethyl benzidine, triazine, and salicylic acid metal complexesmay be cited. Such a charge controlling agent as mentioned above is moreproperly added externally to the resin particles obtained in consequenceof the suspension polymerization than it is added during the course ofthe suspension polymerization.

As concrete examples of the fluidizing agent, inorganic fine particlessuch as colloidal silica, hydrophobic silica, hydrophobic titania,hydrophobic zirconia, and talc and organic fine particles such aspolystyrene beads and (meth)acrylic resin beads may be cited.

The static charge developing toner obtained as described above has anaverage particle diameter in the approximate range of 2-20 μm,preferably 3.5-15 μm, for example, and has uniformly dispersed in thetoner particles thereof an epoxy resin or an epoxy resin and acrystalline (meth)acrylic ester type polymer. The static chargedeveloping toner obtained as described above has a glass transitiontemperature (Tg) generally in the range of 30-100° C., preferably 40-90°C., and more preferably 50-80° C.

The temperature at which the static charge developing toner according tothis invention manifests a thorough fixing property is typically in theapproximate range of 70-200° C., preferably in the approximate range of100-180° C., though it depends on the kind of the main binder resin, theamount of an epoxy resin to be incorporated, and such fixing conditionsas the interfacial pressure (fixing pressure) of the opposed rollers inthe heating roller fixing mechanism, the rotary speed of the rollers(fixing speed), the contact width of the rollers (nip width), and thematerial of the rollers.

Static charge developing toner (2)

The static charge developing toner according to this invention can beobtained not only by the melting and kneading method using the epoxyresin-including binder resin and/or the epoxy resin- and crystalline(meth)acrylic ester type polymer-including bind resin as the binderresin component as described in the section "static charge developingtoner (1)" above but also by the method of direct production based onthe suspension polymerization.

To be specific, the static charge developing toner according to thisinvention can be obtained by suspending in an aqueous medium thepolymerizable monomer composition obtained by dispersing or dissolvingthe epoxy resin, which is, for example, supplied in the form of beads,in the polymerizable monomer and polymerizing the suspendedpolymerizable monomer composition, when necessary, together with afurther incorporated polymerizable monomer in the presence of a coloringagent and/or a magnetic powder at a temperature in the range of 50-90°C., preferably 60-80° C., for example.

The other static charge developing toner according to this invention canbe obtained by suspending in an aqueous medium the polymerizable monomercomposition obtained by dispersing or dissolving the epoxy resin, whichis, for example, supplied in the form of beads, and the crystalline(meth)acrylic ester type polymer in the polymerizable monomer andpolymerizing the suspended polymerizable monomer composition, whennecessary, together with a further incorporated polymerizable monomer inthe presence of a coloring agent and/or a magnetic powder at atemperature in the range of 50-90° C., preferably 60-80° C., forexample.

During this suspension polymerization, the polymerizable monomercomponent may incorporate therein other polymer such as, for example, apolyester and may suitably incorporate further therein such knownadditives as a chain transfer agent serving to adjust the degree ofpolymerization. During the course of the suspension polymerization, across-linking agent may be incorporated and other components such as theoffset-preventing agent and the charge controlling agent which areincorporated, when necessary, in the toner may be present in thepolymerization system. Incidentally, the charge controlling agent ismore properly added externally to the resin particles obtained inconsequence of the suspension polymerization than it is added during thecourse of the suspension polymerization.

The specific examples and the amounts of addition of the polymerizablemonomer, epoxy resin, crystalline (meth)acrylic ester type polymer,coloring agent, and magnetic powder to be used in the production of thestatic charge developing toner according to this invention by the methodof suspension polymerization described above and those of other polymer,chain transfer agent, cross-linking agent, dispersion stabilizer,polymerization initiator, offset-preventing agent, and chargecontrolling agent to be optionally incorporated are substantially thesame as those already described and will be omitted from the followingdescription.

The amount of the epoxy resin to be incorporated, though notspecifically limited, is slightly smaller than that involved in theproduction of the binder resin described above. Properly, this amount issuch that the content of the epoxy resin may be in the range of 1-20%,preferably 2-10%, based on the total weight of the toner. The reason forthis range is that in the direct production of the toner particles bythe method of suspension polymerization, the conditions for thepolymerization are liable to become severe owing to the presence of suchsubstances as the coloring agent in the polymerizable monomercomposition. By the same reason, the amount of the crystalline(meth)acrylic ester type polymer to be incorporated is properly suchthat the content of this polymer may fall in the range of 5-15%,preferably 1-10%, based on the total weight of the binder resin.

Since the suspension polymerization is intended for allowing the coloredparticles produced thereby to be directly used as toner particles, thereaction is appropriately performed either after the particle diameterof the suspended particles has been controlled or while the particlediameter is being controlled. It is particularly favorable to performthe reaction after the control of the particle diameter has beencompleted. This control of the particle diameter is effected, forexample, by stirring the suspension having the prescribed componentdispersed in an aqueous medium by the use of the T. K. Homomixer. It maybe otherwise effected by passing the suspension at least once throughsuch a high-speed stirrer as the line mixer (such as, for example, EbaraMilder). In consequence of this control of the particle diameter, thesuspended particles prior to the suspension polymerization acquire anaverage particle diameter in the approximate range of 2-20 μm,preferably 3.5-15 μm.

The coloring agent and/or the magnetic powder may be added to thepolymerizable monomer composition at the same time that the epoxy resinis added or at a different time from that of the addition of the epoxyresin. The same remarks hold good for the crystalline (meth)acrylicester polymer and for other additives which are used when necessary.

After the suspension polymerization is completed, the colored particlesconsequently obtained are separated from the aqueous medium, dried, andoptionally classified. Then, the colored particles can be used as tonerparticles either directly or after external addition of known additivessuch as the fluidizing agent and the charge controlling agent.

The static charge developing toner obtained by the method of suspensionpolymerization as described above assume the shape of spheres capable ofcontrolling the average particle diameter in the range of 2-20 μm,preferably 3.5-15 μm and the particle diameter distribution in the rangeof 0-80%, preferably 1-50% of the coefficient of variation of particlediameter. In the individual toner particles, the epoxy resin or both theepoxy resin and the crystalline (meth)acrylic ester type polymer areuniformly dispersed.

The toner which is obtained by the method of suspension polymerizationis equal or superior to the toner obtained by the melting and kneadingmethod mentioned above in terms of such properties as the glasstransition point (Tg) and the fixing property.

Now, this invention will be described more specifically below withreference to working examples. It should be noted, however, that thisinvention is not limited by the following examples. The terms "part" and"%" to be used in the following examples and controls refer to thoseexpressed by weight unless otherwise specified.

EXAMPLE 1

A reaction kettle provided with a stirrer, an inert gas inlet, a refluxcondenser, and a thermometer was charged with 3000 parts of deionizedwater having 1 part of polyvinyl alcohol dissolved in advance therein.To the deionized water in the reaction kettle was added a mixtureprepared in advance by dissolving 100 parts of benzoyl peroxide in apolymerizable monomer consisting of 850 parts of styrene and 150 partsof n-butyl acrylate. They were stirred at a high speed to form ahomogeneous suspension. Subsequently, the suspension was blown withnitrogen gas and heated to 85° C. and continuously stirred at thistemperature for five hours to effect a polymerization reaction. Then,the reaction mixture was deprived of water to obtain a low molecularpolymer having Mn=4700 and Mw=14000.

The same reaction kettle as mentioned above was charged with 8500 partsof deionized water having 5 parts of sodium dodecyl benzene sulfonatedissolved in advance therein as an anionic surfactant. To the deionizedwater in the reaction kettle was added a mixture which was prepared inadvance by combining 100 parts of an epoxy resin of an epoxy equivalentof 435-485 g/equivalent weight (produced by Asahi Ciba K.K. and marketedunder trademark designation of "Araldite AER6071"), 350 parts of the lowmolecular weight polymer mentioned above, 50 parts of polyethylene wax(Mn=2000), 30 parts of azobisisobutyronitrile, and 30 parts of2,2'-azobis(2,4-dimethyl valeronitrile) with a polymerizable monomercomponent consisting of 822 parts of styrene, 175 parts of n-butylacrylate, and 3 parts of divinyl benzene. They were stirred at 8000 rpmfor five minutes by the use of a T. K. Homomixer (produced by TokushuKika Kogyo K.K.) to form a homogeneous suspension.

Then, the suspension was blown with nitrogen gas and heated to 70° C.and continuously stirred at this temperature for five hours to effect asuspension polymerization reaction. After the reaction, the suspendedparticles were separated by filtration and dried to obtain an epoxyresin-including binder resin (1) having Mn=7500 and Mw=122000.

In a Laboplastmill, 90 parts of the epoxy resin-including binder resin(1), 10 parts of carbon black (produced by Mitsubishi ChemicalIndustries, Ltd. and marketed under product code of "MA-100R"), and 2parts of a charge controlling agent (produced by Hodogaya Chemical Co.,Ltd. and marketed under trademark designation of "Aizen Spilon BlackTRH") were kneaded at 100° C. for 30 minutes. The resultant blend waspulverized coarsely to below 1 mm and then finely pulverized with a jetmill and classified with a wind classifier, to obtain a static chargedeveloping toner master powder (1) having an average particle diameterof 7.16 μm. A static charge developing toner (1) was obtained by adding0.3 part of a hydrophobic aerosil (produced by Nippon Aerosil K.K. andmarketed under product code of "R972") to 100 parts of the static chargedeveloping toner master powder (1) and uniformly dispersing the addedaerosil.

This static charge developing toner (1) was tested for glass transitionpoint (Tg), melt flow point by a flow tester, and offset property andfixing ratio by an actual machine test. The results are shown in Table1.

In Table 1, T_(fb) represents the temperature at which the sample tonermelted and began to flow in a flow tester used thereon for measurement,T_(1/2) represents the temperature at which one half of the whole amountof the sample toner placed in the tester flowed, and T_(end) representsthe temperature at which the whole amount of the sample flowed, and thelower limit of the fixing temperature represents the level below whichlow temperature offset occurred and the upper limit of the fixingtemperature represents the level above which high temperature offsetoccurred.

EXAMPLE 2

An epoxy resin-including binder resin (2) was obtained by repeating theprocedure of Example 1 while using 50 parts of stearyl acrylate polymer(Mw=35000) in the place of 50 parts of polyethylene wax.

This resin had a molecular weight, Mn=7300 and Mw=135000. A staticcharge developing toner (2) having an average particle diameter of 8.25m was obtained by following the procedure of Example 1 while using theepoxy resin-including binder resin (2) instead. This static chargedeveloping toner (2) was tested for toner properties in the same manneras in Example 1. The results are shown in Table 1.

Control 1

A toner binder resin (C1) for comparison having a molecular weight,Mn=9300 and Mw=123000, was obtained by repeating the procedure ofExample 1 while omitting the incorporation of the epoxy resin.

A static charge developing toner (C1) for comparison having an averageparticle diameter of 7.28 μm was obtained by following the procedure ofExample 1 while using 90 parts of the toner binder resin (C1) forcomparison, 10 parts of carbon black (produced by Mitsubishi ChemicalIndustries, Ltd. and marketed under product code of "MA-100R"), and 2parts of a charge controlling agent (produced by Hodogaya Chemical Co.,Ltd. and marketed under trademark designation of "Aizen Spilon BlackTRH") instead.

This static charge developing toner (C1) for comparison was tested forthe toner properties in the same manner as in Example 1. The results areshown in Table 1.

Control 2

A static charge developing toner (C2) for comparison having an averageparticle diameter of 6.95 μm was obtained by repeating the procedure ofExample 1 while using 84 parts of the toner binder resin (C1) forcomparison, 6 parts of an epoxy resin of an epoxy equivalent of 435-485g/equivalent weight (produced by Asahi Ciba K.K. and marketed undertrademark designation of "Araldite AER6071"), 10 parts of carbon black(produced by Mitsubishi Chemical Industries, Ltd. and marketed underproduct code of "MA-100R"), and 2 parts of a charge controlling agent(produced by Hodogaya Chemical Co., Ltd. and marketed under trademarkdesignation of "Aizen Spilon Black TRH") instead.

This static charge developing toner (C2) for comparison was tested forthe toner properties in the same manner as in Example 1. The results areshown in Table 1.

EXAMPLE 3

A reaction kettle provided with a stirrer, an inert gas inlet, a refluxcondenser, and a thermometer was charged with 2000 parts of deionizedwater having 1 part of polyvinyl alcohol dissolved in advance therein.To the deionized water in the reaction kettle, a mixture prepared inadvance by dissolving 80 parts of benzoyl peroxide in a polymerizablemonomer consisting of 585 parts of styrene, 390 parts of butylmethacrylate, and 25 parts of glycidyl methacrylate was added. They werestirred at a high speed to form a homogeneous suspension. Subsequently,the suspension was blown with nitrogen gas and heated to 80° C. andcontinuously stirred at this temperature for five hours to effect apolymerization reaction. Then the resultant reaction mixture wasdeprived of water to obtain a polymer having epoxy group(s) as reactivegroup(s).

By the use of a pressure kneader, 400 parts of the polymer having theepoxy group(s) as reactive group(s), 150 parts of carbon black (producedby Mitsubishi Chemical Industries, Ltd. and marketed under product codeof "MA-100R"), and 50 parts of a charge controlling agent (produced byHodogaya Chemical Co., Ltd. and marketed under trademark designation of"Aizen Spilon Black TRH") were kneaded under the conditions of 160° C.and 100 rpm to effect a reaction. The resultant reaction mixture wascooled and pulverized, to obtain a carbon black graft polymer as acoloring agent.

The same reaction kettle as mentioned above was charged with 8970 partsof deionized water having 5 parts of sodium dodecyl benzene sulfonatedissolved in advance therein as an anionic surfactant. To the deionizedwater in the reaction kettle was added a mixture which was prepared inadvance by combining 100 parts of an epoxy resin of an epoxy equivalentof 435-485 g/equivalent weight (produced by Asahi Ciba K.K. and marketedunder trademark designation of "Araldite AER6071"), 500 parts of thecarbon black graft polymer mentioned above as a coloring agent, 40 partsof polyethylene wax (Mn=2000), 30 parts of azobisisobutyronitrile, and30 parts of 2,2'-azobis(2,4-dimethyl valeronitrile) with a polymerizablemonomer component consisting of 825 parts of styrene, 175 parts ofn-butyl acrylate, and 2 parts of divinyl benzene. They were stirred at8000 rpm for five minutes by the use of a T. K. Homomixer (produced byTokushu Kika Kogyo K.K.) to form a homogeneous suspension.

Then, the suspension was blown with nitrogen gas and heated to 70° C.and continuously stirred at this temperature for five hours to effect asuspension polymerization reaction, to obtain a suspension of finecolored spherical particles. The particles were separated by filtrationand dried, to obtain fine colored particles (3) having an averageparticle diameter of 7.14 μm.

The colored particles (3) were used in their unmodified form as a toner.The toner was tested for glass transition point (Tg), melt flow point bya flow tester, and offset property and fixing ratio by an actual machinetest. The results are shown in Table 2.

In Table 2, T_(fb), T_(1/2), and T_(end), and the lower limit of thefixing temperature, and the upper limit of the fixing temperature havethe same meanings as those shown in Table 1.

EXAMPLE 4

Fine colored particles (4) having an average particle diameter of 7.36μm were obtained by repeating the procedure of Example 3 while changingthe amount of styrene to 800 parts and that of n-butyl acrylate to 200parts.

The colored particles (4) were used in their unmodified form as a toner.The toner was tested for the toner properties in the same manner as inExample 3. The results are shown in Table 2.

EXAMPLE 5

Fine colored particles (5) having an average particle diameter of 6.81μm were obtained by repeating the procedure of Example 3 while using 40parts of stearyl acrylate polymer (Mw=35000) in the place of 40 parts ofpolyethylene wax.

The colored particles (5) were used in their unmodified form as a toner.The toner was tested for the toner properties in the same manner as inExample 3. The results are shown in Table 2.

Control 3

Fine colored particles (C3) for comparison having an average particlediameter of 7.17 μm were obtained by repeating the procedure of Example3 while changing the amount of styrene to 880 parts, that of n-butylacrylate to 220 parts, and that of the epoxy resin to 0.

The colored particles (C3) were used in their unmodified form as atoner. The toner was tested for the toner properties in the same manneras in Example 1. The results are shown in Table 1.

The properties were rated as follows.

Glass transition point (Ta)

This was determined by the method for measuring differential scanningcalorimetry(DSC).

Melt flow property

This property was determined by the use of a flow tester (produced byShimadzu Seisakusho Ltd. and marketed under trademark designation of"SHIMADU FLOWTESTER (CAPILLARY RHEOMETER) CFT-500C") under theconditions of cylinder pressure 20.0 kgf/cm², die L: 1.00 mm and D: 0.50mm, shear stress 2.451×10⁶ dynes/cm², and temperature increase rate 6.0°C./minute.

Nonoffset range

A sample was used in a copying device (a modified machine of "Leodry7610", Toshiba) to produce an unfixed image having an image density ofabout 1.2. Then, the unfixed image was passed through a heat rollerfixing device (a modified machine of "U-Bix 1805MR", Konica) to obtain afixed image, with the fixing temperature varied to determine thepresence or absence of a low temperature offset and a high temperatureoffset.

Fixing ratio

A sample was used in the same manner as in the rating of the nonoffsetrange to obtain fixed images at varying temperatures. The fixed imageswere tested for image density by the use of a densitometer (Macbeth RD914). Then, by the use of an abrasion resistance tester (produced bySuga Shikenki K.K.), the fixed images were subjected to a test forabrasion resistance performed by rubbing them with a PPC cleaning padreciprocated thereon five times. The images, after the test, weremeasured for image in the same manner as above. The fixing ratio at avarying temperature was calculated from the following formula using theimage densities before and after the abrasion resistance test todetermine the temperatures at which the fixing ratios of 70% (lowestfixing temperature) and 90% were obtained.

Fixing ratio (%)=(Image density after the abrasiontest/image densitybefore the abrasion test)×100

Resistivity, log ρ

This was determined by the use of an automatic dielectric loss tester(produced by Ando Denki K.K. and marketed under product code of"TR-1100").

                                      TABLE 1    __________________________________________________________________________                       Example 1                             Example 2                                   Control 1                                          Control 2           Binder resin                       (1)   (2)   (C1)   (C2)    __________________________________________________________________________    Ratio of toner           (Ratio of combination of    combination           (binder resin)           Poly(styrene-butyl acrylate)                       60 parts                             60 parts                                   64.3                                       parts                                          60 parts           Low molecular polymer                       21 parts                             21 parts                                   32.5                                       parts                                          21 parts           Polyethylene wax                       3  parts                             --    3.2 parts                                          3  parts           stearyl acrylate polymer                       --    3  parts                                   --     --           Expoxy resin                       6  parts                             6  parts                                   --     --           Epoxy resin --    --    --     6  parts           Carbon black                       10 parts                             10 parts                                   10  parts                                          10 parts           Charge controlling agent                       2  parts                             2  parts                                   2   parts                                          2  parts    Thermal           Glass transition point (Tg)                       61.2° C.                             62.7° C.                                   60.6° C.                                          59.8° C.    properties           Melt flow                 T.sub.fb                       106.0° C.                             107.2° C.                                   106.4° C.                                          103.9° C.           property                 T.sub.1/2                       131.9° C.                             132.7° C.                                   132.3° C.                                          130.3° C.                 T.sub.end                       136.6° C.                             139.9° C.                                   137.1° C.                                          135.1° C.    Fixing Nonoffset                 Lower limit                       125° C.                             125° C.                                   125° C.                                          125° C.    properties           range of fixing                 temperature                 Upper limit                       225° C.                             ≦230° C.                                   210° C.                                          205° C.                 of fixing                 temperature           Fixing property 70% of                       135° C.                             135° C.                                   140° C.                                          135° C.           fixing ratio           Fixing property 90% of                       140° C.                             140° C.                                   150° C.                                          145° C.           fixing ratio    Electric           State of dispersion of                       uniform                             uniform                                   uniform                                          not    properties           carbon black (by TEM           uniform           photography)           Resistivity log ρ                       11.1  11.1  11.1   10.8    __________________________________________________________________________

By comparing the results of Example 1 and Control 1 shown in Table 1, itis confirmed that the product of Example 1 containing an epoxy resin inconsequence of the incorporation of an epoxy resin-including binderresin had an enlarged nonoffset range, enjoyed mild fixing conditionsdemanded by such means as a copying device, and permitted fixation at alow temperature as compared with the product of Control 1 containing noepoxy resin. The product of Example 2 containing stearyl acrylatepolymer in combination with an epoxy resin had a larger nonoffset rangethan the product of Example 1. The product of Control 2 containing anepoxy resin in the same amount as the product of Example 1, thoughenjoying a slight improvement in the low-temperature fixing property,had a rather narrow nonoffset range and imposed severe fixing conditionson a copying device, for example, as compared with the product ofControl 1. It further suffered ununiform dispersion of carbon black (CB)and had the possibility of dispersing the charging property and thefixed image density.

                  TABLE 2    ______________________________________               Example 3                      Example 4                               Example 5                                        Control 3    ______________________________________    Fine colored particles                 (3)      (4)      (5)    (C3)    Glass transition point                  59.6° C.                           57.0° C.                                    60.6° C.                                           59.1° C.    (Tg)    Melt flow           T.sub.fb  107.9° C.                              106.6° C.                                     108.5° C.                                            108.4° C.    property           T.sub.1/2 142.4° C.                              138.1° C.                                     144.1° C.                                            139.2° C.           T.sub.end 151.4° C.                              144.4° C.                                     153.3° C.                                            145.7° C.    Nonoffset           Lower limit                     130° C.                              120° C.                                     120° C.                                            125° C.    range  of fixing           temperature           Upper limit                     ≦230° C.                              220° C.                                     ≦230° C.                                            225° C.           of fixing           temperature    Fixing 70% of    130° C.                              120° C.                                     125° C.                                            130° C.    property           fixing ratio           90% of    140° C.                              125° C.                                     135° C.                                            140° C.           fixing ratio    ______________________________________

By comparing the results of Example 3 and Control 3 whose toners werenearly equal in Tg as shown in Table 2, it is found clearly that theproduct of Example 3 which lowered Tg by the incorporation of an epoxyresin showed an enlarged nonoffset range and allowed mild fixingconditions imposed on a copying device. By comparing the results ofExample 4 and Control 3 whose toners had nearly equal nonoffset rangesas shown in Table 2, it is clearly noted that the product of Example 4which lowered Tg by the incorporation of an epoxy resin attained aprescribed fixing ratio at a lower temperature and excelled infixability at low temperatures. By comparing the results of Example 5and Control 3 shown in Table 2, it is clearly found that the product ofExample 5 which incorporated therein an epoxy resin and stearyl acrylatepolymer enjoyed an enlarged nonoffset range and accomplished aprescribed fixing ratio at a still lower temperature in spite of a highTg.

Industrial Applicability

The epoxy resin-including binder resin of this invention, as describedabove, is obtained by polymerizing a polymerizable monomer in thepresence of an epoxy resin. The static charge developing toner producedby using this epoxy resin-including binder resin as at least part of thebinder resin component thereof enables a fixed image stable at lowtemperatures to be formed without entailing offset.

The epoxy resin and crystalline (meth)acrylic ester typepolymer-including binder resin of this invention is obtained bypolymerizing a polymerizable monomer in the presence of an epoxy resinand a crystalline (meth)acrylic ester type polymer. The static chargedeveloping toner produced by using this epoxy resin and crystalline(meth)acrylic ester type polymer-including binder resin as at least partof the binder resin component thereof enables a fixed image stable atstill lower temperatures to be formed with the nonoffset range furtherenlarged as compared with the epoxy resin-including binder resin.

The toner of this invention is obtained by using the epoxyresin-including binder resin and/or the epoxy resin and crystalline(meth)acrylic ester type polymer-including binder resin as at least partof the binder resin component thereof. Probably because the uniformdispersion of the epoxy resin in the toner particles is consequentlyensured, this toner enjoys excellent stability during storage even whenthe epoxy resin used therein has a relatively low molecular weight and arelatively low Tg (such as, for example, about 30-60° C.) and manifestsfully satisfactory properties as compared with the toner which isobtained by simply melting and kneading with an epoxy resin a binderresin including no epoxy resin. When the epoxy resin and crystalline(meth)acrylic ester type polymer is used, the synergistic effect offurther exalting the effect of fixing the toner at low temperatures andenlarging the nonoffset range as well is attained.

The toner of this invention is also obtained by suspension polymerizingin an aqueous medium the polymerizable composition containing apolymerizable monomer and a coloring agent and/or a magnetic powder inthe presence of an epoxy resin or in the presence of an epoxy resin anda crystalline (meth)acrylic ester type polymer. This toner likewiseenables a fixed image stable at low temperatures to be formed withoutentailing offset.

The static charge developing toner obtained with the toner binder resinaccording to this invention, therefore, is fit for embodying the effortsto lower power consumption and heighten operational speed in the fieldof electrophotography, static recording, and static printing.

We claim:
 1. A toner binding resin comprising a polymer obtained bypolymerizing a polymerizable monomer in the presence of an epoxy resinand a crystalline (meth)acrylic ester polymer, wherein said bindingresin contains 1-25% of said epoxy resin and 0.5-20% of said crystalline(meth)acrylic ester polymer, based on the total weight of said bindingresin.
 2. A toner binder resin according to claim 1, wherein said epoxyresin has an epoxy equivalent in the range of 100-1000 g/equivalentweight.
 3. A toner binder resin according to claim 1, wherein saidpolymerizable monomer is a styrenic monomer, a (meth)acrylic ester typemonomer, or a combination thereof.
 4. A toner binder resin according toany of claims 1, 2 and 3, wherein said binder resin is obtained bysuspension polymerizing in an aqueous medium a polymerizable monomercomposition containing at least said polymerizable monomer, said epoxyresin, and said crystalline (meth)acrylic ester polymer, wherein saidepoxy resin and said crystalline (meth)acrylic ester type polymer beinguniformally dispersed in said polymerizable monomer.
 5. A static chargedeveloping toner, characterized by using the toner binding resin setforth in any of claims 1-3 as part of at least the binding resincomponent, wherein said toner contains 0.5-25% epoxy resin, based on thetotal weight of said toner, and 0.5-20% of said crystalline(meth)acrylic ester polymer, based on the total weight of said bindingresin component.
 6. A static charge developing toner comprising apolymer obtained by suspension polymerizing in an aqueous medium apolymerizable monomer composition containing a polymerizable monomer, acoloring agent, and, optionally, a magnetic powder in the presence of anepoxy resin and a crystalline (meth)acrylic ester type polymer, whereinsaid toner contains 1-20% of said epoxy resin, based on the total weightof said toner, and 5-15% of said crystalline (meth)acrylic esterpolymer, based on the total weight of said binding resin component.
 7. Atoner binder resin according to claim 2, wherein said polymerizablemonomer is a styrenic monomer, a (meth)acrylic ester type monomer, or acombination thereof.